Contents:
License Conditions and Software Compatibility
Introduction
Contents and File Name Conventions
File Format
Source Information

Software Compatibility - These BYTES of the BIG APPLE files conform to vendor specific formats of MapInfo® Tables and Interchange Files and ESRI^® Shapefiles. These files are data files, not programs. The user will require a GIS (Geographic Information System), CAD (Computer Assisted Design or Drafting), mapping, or other software package which can import the above file types. The BYTES of the BIG APPLE files have not been tested with every package that claims to import the above files.

Introduction
The BYTES of the BIG APPLE geographic base map files are maintained, and new releases are periodically produced, by the Geographic Systems Section of the Department of City Planning's (DCP) Information Technology Division. These files can be imported into a wide variety of Geographic Information System software products to produce computer-generated maps and to perform spatial analysis. The BYTES of the BIG APPLE files consist of the DCPLION single line street base map; a set of district boundary polygon files for various types of administrative and political districts; and tax block and tax lot base map files. DCPLION is a digital map of New York City representing the city's streets and other geographic features such as shorelines, surface rail lines, and census block boundaries, along with feature names and address ranges for each addressable street segment. The administrative and political district boundary files overlay on DCPLION. The tax block and lot files contain the city's tax block and lot boundary polygons, block numbers (or lot numbers) and street names.

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Contents and File Name Conventions
Each compact disk contains a set of the following files in two formats: MapInfo® Tables and ESRI® Shapefiles.

Tax Block and Lot: Each format represents tax blocks and lots both clipped to the shoreline and unclipped including submerged tax geographies in one of New York City's five boroughs: The Bronx, Brooklyn, Manhattan, Queens and Staten Island. Each tax block or tax lot polygon has one attribute identifying the block number or BBL (borough, block and lot) number the polygon defines. Tax Block and Tax Lot numbers are unique in each borough and assigned by the Department of Finance (DOF).   In addition, there is a BoroCode attribute that indicates the borough in which the block or lot is located.

The tax block number consists from one to five digits; for example, 486 and 10012 are valid tax block numbers. In a very few cases, DCP has assigned 'stand-in' tax block numbers for polygons representing tracts of land that do not have a DOF tax block number. Examples are traffic islands in Park Avenue (Manhattan) and Pelham Parkway (The Bronx). In these cases, the assigned numbers are unique within a borough and are numbered to be much higher than the range of valid tax block numbers in the borough; the numbers assigned start with 20000.

The BBL number is a concatenation of the borough, block and lot number. It contains 10 digits.  The leftmost digit is the borough code;the next five digits represent the block number; the four rightmost digits are the lot number.

In a very few cases, Department of City Planning has assigned 'stand-in' tax lot identifiers for polygons representing tracts of land that do not have a DOF tax lot number. These occur where DCP has also assigned 'stand-in' block numbers (See above). In these cases, the assigned numbers are unique within a borough and are numbered to be much higher than the range of valid tax lot numbers in the borough; 200259999 is a valid 'stand-in' tax lot identifier.

Each condominium unit is considered a tax lot by the City and is assigned a unique tax lot number. The Tax Block and Lot Base Map files and BYTES of the BIG APPLE files do not contain graphic records for each condominium unit. Instead, a tax lot polygon is created to represent the entire condominium development. The tax lot number assigned to this polygon is the Department of Finance’s billing lot number.  In a very few cases, the numerically lowest tax lot number of all the units in the condominium is used.

The initial two letters of each file identifies the borough where the files are located as follows:

The next two letters represent the geography contained in the file as follows:

For files that are clipped to the shoreline the four letter file name will be followed by the word: "CLIP".

For example, the file named "bx_cd.shp" represents the Community District Boundaries of the Bronx in an ESRI® shapefile format. The file named "bk_tl_clip.tab" represents the Brooklyn Tax Lot geography clipped to the shoreline in a MapInfo® Table format.

Marble Hill and Rikers Island: Marble Hill is a neighborhood that is part of the Borough of Manhattan but is administratively often included with neighboring areas of The Bronx. Parts of Marble Hill are within Bronx Community District 7; the rest is within Bronx Community District 8. Marble Hill blocks and lots are included on the Manhattan CD-ROM as part of the MN block and lot files. They are also included as separate Marble Hill files on the Bronx CD-ROM.

Similar to the Marble Hill situation is that of Rikers Island. Rikers Island is part of the Borough of The Bronx. However, it is administratively included in Queens Community District 1. Therefore, Rikers Island is included on both The Bronx and Queens CD-ROMs.

Community Districts: This feature class represents the boundaries of community districts and joint interest areas within each borough. Each CD-ROM contains the Community Districts and Joint Interest Areas clipped to the shoreline and unclipped including submerged tax geographies.

Borough Boundary: This feature class represents the boundaries of the borough for each CD-ROM. Each CD-ROM contains the borough boundary clipped to the shoreline and unclipped showing the entire legal boundary of each borough.

Street Annotation: in MapInfo, the street name annotation feature class is composed of annotation objects. In Shapefiles, streetnames are distributed as point features with one field containing the streetname and another field containing the text angle.

File Format
Geometry: Each discrete graphic object within each file type is called an object or geometry. Each object is of a particular geometry type. Examples of geometry type are polygon, line, point and annotation.

The outlines of the lots and blocks are defined as polygons. A polygon is composed of a set of individual line segments that form a closed boundary around a particular region. If a group of polygons is grouped together to form one object, the resultant object is called a complex polygon. Each block, lot, borough boundary, and community district is composed of one or more polygons grouped together.

Attributes:GIS file types support relationships between tabular database information and graphic objects or geometries. Associated information, which can be either graphic or non-graphic, is stored or related within each object's attribute record. In the BYTES of the BIG APPLE files on these disks, all objects in the block or lot feature class have two attributes. BoroCode indicates the borough of the block or lot.  (1 = Manhattan, 2 = The Bronx, 3 = Brooklyn, 4 = Queens, 5 = Staten Island.) The second attribute is called TaxBlock or BBL and contains either the tax block number or the borough, block and  lot number.

Source Information
Map Sources: These files are derived from the Department of City Planning (DCP) Tax Block and Tax Lot geography files ( Tax Block and Lot Base Map). These files are digitized and maintained by the DCP Information Technology Division/Geographic Systems Section. The primary sources for these files are Department of Finance tax maps. These files are schematic representations of the tax block and lot outlines.

The files should not be used for applications that require precise measurements.

Coordinate System / Units of Measurement: The coordinates of blocks and lots in these files are expressed in units of feet. The coordinate system used for the entire City is the New York Long Island State Plane Coordinate System (FIPS 3104) Feet, North American Datum 1983 (NAD83). The approximate ranges of coordinate values for the City are:

X-coordinate (East-West): minimum: 909900; maximum: 1067600
Y-coordinate (North-South): minimum: 117500; maximum: 275000

Spatial Accuracy: The Tax Block and Lot Base Map files were created for planning applications at DCP. High spatial accuracy was not of primary concern in their creation. A limited set of control points were used to loosely fit the files to New York Long Island State Plane Coordinate System.

The New York City Tax Blocks have been conflated to the NYCMap planimetric features.

Temporal Accuracy: The Tax Block and Lot Base Map files are maintained in an update cycle in which changes mapped by the Department of Finance are incorporated into Tax Block and Lot Base Map. The current release of the Tax Block and Tax Lot Base Map files, 06C, includes updates through October 2006.

Legal vs. Physical Features: These files are a representation of the City's tax blocks and lots. Tax blocks are not necessarily identical to physical blocks. Boundaries of tax blocks are not usually located at the curb line of a street. Many properties include areas under bodies of water. Most highways and many other public features are not represented in these files because their depiction does not arise from the delineation of tax lots.